The UK Is Building Its Own AI, and Defense Giants Are All In

A coalition of Britain’s largest defense, banking, and infrastructure institutions has signed on to help build the country’s first sovereign frontier AI model. This move will have direct implications for the defense and aerospace primes gathering at Farnborough this year.

Cosine, the Y-Combinator-backed AI company, is at the helm of this coalition. The company develops agentic software agents designed to assist in application development. However, unlike most IDEs, which are trained mainly on newer technologies, Cosine’s agent also has unparalleled proficiency in legacy platforms primarily utilized by defense agencies: think Ada, Assembly, and Fortran.

Cosine confirmed that BAE Systems, Babcock International Group, Thales UK, Leonardo UK and Telefónica Tech UK&I have joined BT, HSBC, Lloyds Banking Group, LSEG, NatWest Group and PwC in signing memoranda of understanding to co-design the contracted AI model, named Lumen Sovereign. The Alan Turing Institute, QineitQ, and Era4 round out the coalition.

Lumen Sovereign will train the model on Isambard-AI, one of Europe's most powerful supercomputers, using compute allocated through the UK Government's £500 million Sovereign AI program. The model will support mission-critical organizations that have realized that dependence on AI developed in other countries constitutes an unacceptable risk. After recent developments in accessibility to models like Fable 5 and Mythos, this has become even more critical. 

The company is targeting deployment readiness by the end of 2026.

For the defense contractors in the coalition, the pitch centers on operating in classified and air-gapped environments where relying on foreign-built AI has not been viable. BAE Systems Group CTO Rob Merryweather framed the collaboration as a way to strengthen the UK’s industrial base while keeping the company at the forefront of sovereign AI adoption.

He said, “Lumen Sovereign provides an encouraging example of innovation in practice - applying cutting-edge technology to critical sectors while strengthening the UK’s sovereign AI capability. Working with start-ups such as Cosine presents an important opportunity to support innovation across the defence ecosystem, while positioning BAE Systems at the forefront of adoption. This collaborative approach helps to nurture a more dynamic and resilient UK industrial base."

Cosine CEO Alistair Pullen has been blunt about the commercial logic behind the effort, arguing that dependence on foreign AI providers carries risks that UK institutions are no longer willing to accept. “AI is the single most important technology of our generation. Enterprises are increasingly waking up to the risk of being wholly dependent on foreign providers for this technology.”

Priority use cases are being developed in collaboration with the coalition. These include cybersecurity and adversarial testing, clinical trial coordination, legal document review, and healthcare administration, spanning more than 30 regulated industry workflows.

With defense spending and sovereign technology on the agenda at Farnborough this year, the scale of this coalition signals how seriously the UK’s largest institutions are now prioritizing sovereign AI as critical national infrastructure.

To learn more about Cosine and Lumen Sovereign, visit booth 4238J in the Defense SME Zone at the Farnborough Airshow or https://cosine.sh.